An image forming apparatus, such as a copying machine, MFP or printer, forms images on recording media. The recording media include a plurality of types of recording media such as cardboards, plain paper and OHP films.
To form high quality images, the image forming apparatus optimizes conditions of an image forming method and fixing method according to the type of recording media. Therefore, information related to the type of the recording media, for example, information such as the type, thickness and density of the recording media, is required.
A conventional image forming apparatus has sensors, such as an optical sensor and thickness sensor for deciding the type of the recording media, between a recording media supplying unit arranged in a conveying path of recording media and the image forming portion. The image forming apparatus of this type supplies recording media from the recording media supplying unit and decides on the type of the recording media while the recording media are conveyed.
However, if the type of recording media is decided after the recording media are supplied from the recording media supplying unit, some image forming apparatuses cannot optimize the conditions of the image forming method and fixing method in time.
In this regard, a technique is proposed, in which light on the bundle of recording media stacked in the recording media supplying unit is radiated in order to let the light in the bundle, an image of light leaking from between these stacked recording media is captured by means of an area sensor, and the thickness and density of the recording media is measured based on contrast of the obtained image and a change of a light intensity, that is, the attenuation rate of the light in the recording media in a radiating direction.
However, when point light sources such as round type LEDs are used for the light sources for radiating light toward recording media, unevenness of the light intensity is produced in a detection area of an area sensor. This unevenness of the light intensity limits precision to decide on the type of recording media.
Hence, a recording media deciding apparatus, image forming apparatus and recording media deciding method which can more precisely decide on the type of recording media when the recording media are in the recording media supplying unit are required.